The invention relates to planetary transmissions of the type disclosed in U.S. Pat. No. 3,540,311 granted Nov. 11, 1970 to C. W. Chillson. This prior patent discloses a planetary transmission in which the planetary elements are not provided with the usual support bearings which constrain the planetary elements against radial and tilting movements. Instead, each of the planetary elements of the transmission include a plurality of axially-spaced gears which are so spaced along the spindle of its planetary element that the net turning moment exerted by the input, output and reaction forces tending to tilt said element out of its radial plane is substantially zero. By said "radial plane" of a planetary element is meant a plane including the transmission axis and the axis of said element. In addition, the transmission includes floating rings having rolling contact with the spindles of the planetary elements to constrain the planetary elements against the radial forces thereon. Such a transmission is herein called a free-floating planetary transmission.
As described in said prior patent, such free-floating planetary transmissions have numerous advantages including the provision of a high speed-ratio reduction at a substantial savings in weight over conventional planetary transmissions. Applicant's assignee has built and successfully operated free-floating planetary transmissions capable of transmitting as much as 750 horsepower.
In many transmission applications, for example in a transmission for driving the propeller of a marine vessel, it generally is desirable to provide a reversible output drive to the propeller. U.S. Pat. No. 3,886,816 granted on June 3, 1975 to DeFeo et al discloses a planetary marine transmission including means for providing the transmission with a reversible output. This prior patent, however, does not disclose a free-floating planetary transmission. Instead, in this prior patent the planet gears are journaled in support bearings on a planet carrier and the two directions of output rotation are obtained by braking either the planet carrier or a gear with which the planet gears are in mesh.
A free-floating planetary transmission has no carrier on which the planet gears are journaled in support bearings. Accordingly, it is not possible to provide a free-floating planetary transmission with a reversible output in a manner similar to that disclosed in the aforementioned DeFeo et al patent.